For many years efforts have been made to develop useable, satisfactory induction heating systems for use in cooking operations. Although the desirability of using induction heating for cooking food and the like has long been recognized, up until fairly recent times induction heating systems have been employed for this type of purpose only very infrequently. The reasons for this are complex and to an extent have to do with consumer resistance possibly related to the heavy cooking utensils previously required for induction cooking.
Ideally, cookware should be lightweight, mechanically strong, corrosion resistant, easy to clean, quick and even heating, wear resistant, of a pleasing appearance and low in cost. To achieve these goals, aluminum and stainless steel has frequently been employed but while both have certain advantages both also suffer disadvantages.
When in addition to the above considerations induction heating capability is taken into account, the problem becomes even more complex. For induction heating to occur, the cookware must be magnetic, at least in part. Thus both aluminum and the non-magnetic stainless steel cannot be used for induction cooking. Cast iron can be used for induction heating cookware but it offers no corrosion resistance, offers uneven heating and is heavy.
Various attempts have been made to overcome these problems using layered or laminated cookware. For example, U.S. Pat. No.3,966,426 teaches a multilayer cookware having a relatively thick,, magnetic, layer to develop the power, a layer of high-thermal conductivity material and a low-magnetic layer. U.S. Pat. No. 3,650,710 attempts to solve the problems using a structure of stainless steel, aluminum and a phosphor-nickel layer.
The present invention, for the first time, solves all of the problems inherent in designing a material for cookware suitable for being induction heated. In particular, the materials of this invention have superior corrosion resistance and they are light in weight.